Paget's Disease

An autosomal dominant condition of abnormal bone remodeling where original osseous tissue is reconstucted through active interplay between excessive bone resorption and abnormal new bone formation 

• may be monostotic or polystotic
• increased osteoclastic bone resorption is the primary cellular abnormality 
• cause is thought to be a virus (intra-nucleur nucleocapsid-like structure)

Peak incidence in the 5th decade of life. common in europeans Phases lytic phase: intense osteoclastic resorption mixed phase: resorption and compensatory bone formation scelotic phase: bone formation predominates Malignancy less than 1% will develop malignant Paget's sarcoma (secondary sarcoma)  osteosarcoma is the most common, followed by fibrosarcoma and chondrosarcoma Paget's sarcoma has a poor prognosis with long term survival of < 20%

Symptoms

• frequently asymptomatic and found incidentally
• pain may be the presenting symptom
• be suspicious for Paget's secondary sarcoma in a patient with a known history of Pagets who complains of new onset intense pain.

Laboratory findings 

• elevated alkaline phosphatase
• elevated hydroxyproline (collagen breakdown marker)
• increased urinary N-telopeptide and alpha-C-telopeptide 

Radiographs show remodeled cortices and coarsened trabeculae which give the bone a blastic appearance Paget's secondary sarcoma shows cortical bone destruction soft tissue mass Bone scan intensely hot in lytic and mixed phase less hot in sclerotic phase

Characteristic histology irregular broad trabeculae with disorganized cement lines  numerous large osteoclastics with multiple nuclei per cell  fibrous vascular tissue interspersed between trabeculae

Treatment

Nonoperative goal of treatment is to inhibit osteoclastic activity pharmocologic treatment includes bisphophonates Didronel is an older generation medication that inhibited osteoclasts and osteoblasts, and therefore could not be used for more that 6 months at a time Pamidronate is a newer generation medication that only inhibits osteoclasts. The disadvantage is that it comes in IV form only calcitonin methotrexate Operative hip and knee arthroplasty often indicated due to joint involvement treat paget's with pharmocologic agents prior to arthroplasty to reduce excessive bleeding Metaphyseal osteotomy and plate fixation  Fractures through pathologic bowing of long bones Impending pathologic fracture of long bone with bowing deformity